Pump units of the type discussed here are generally known. They are used, for example, in transmission housings of a motor vehicle or in other housings where a hydraulic supply is required. Pump units of this kind have a drive shaft, a rotor that cooperates with the drive shaft and that accommodates vanes which slide along a contour ring during a rotation of the rotor, two adjacent vanes enclosing cells which, in response to a rotation of the vanes, increase or decrease in volume, depending on the contour section, and, in the process, suction oil and discharge it again. In addition, a first and a second side plate are provided that are configured to the side of the contour ring. The known transmission pump units have the disadvantage that they tend to come apart during shipping, making it necessary to transport them in a housing or to undertake other measures for securing the same. Another disadvantage of the known pump units having no dedicated housing, is the relatively complex assembly that they require in a transmission housing, for example.